The effect of functionality on the migration behaviors, structural, and dynamical properties of star polymers in Poiseuille flow are investigated by multiparticle collision dynamics integrated with molecular dynamics simulations. Our studies reveal that the star polymer migrates toward the centerline of the cylindrical tube by increasing the flow strength and the degree of inward migration is amplified as the functionality or the number of monomers increases. At high flow strengths, the star polymer with low functionality undergoes a large conformational change due to the tumbling motion, and the tumbling motion is suppressed with increasing functionality, whereas the star polymer with high functionality maintains a steady, stretched state via a trumpet shape. We attribute this phenomenon to the fact that the star polymer with high functionality perturbs the surrounding solvents more strongly at high flow strengths than that with lower functionality, leading to the higher additional hydrodynamic drag forces. These forces are balanced by certain forces in each direction and stabilize the high-functionality star polymer near the centerline due to its trumpet-shaped configuration. Hence, the trumpet structure of star polymers amplifies the inward migration of polymer chains in Poiseuille flow.